Airplane shock absorber



April 14, 1936. F. R. WEYMOUTH lie-19,931

AIRPLANE SHQCK ABSORBER Original Filed April 4. 1927 Jnucufoz Reissue! Apr. 14, 1936 UNITED STATES PATENT OFFICE AIRPLANE SHOCK ABSORBER Delaware Original No. 1,723,963, dated August 6, 1929,

Serial No. 180,851, April 4, 1927.

Application for reissue November "I, 1932, Serial No. 641,688

26 Claims. (Cl. 267-64) This invention relates to shock absorbers and particularly to shock absorbers for the landing chassis of airplanes.

The primary object of the invention is the provision of a shock absorber especially adapted for aircraft use, which incorporates both a liquid damping means for absorbing the initial major shock of landing, and a resilient device for resiliently supporting the load. The resilient device preferably comprises a series of rings having frictionally inter-engaging surfaces which are adapted to slide one on the other, as the friction rings telescope together when a load is applied. Such rings may be in the form of endless bands, presenting slightly tapered friction surfaces of a character which place the bands under radial tensional and compressional strains, when the serig; of rings is compressed in the direction of its a As preferably constructed the shock absorber is in the form of an elongated casing composed of a lower part and an upper part telescopically received therein and of smaller diameter than the lower part, the lower part forming a housing for the series of friction rings and also a container or receptacle for a quantity of damping liquid which substantially fills the lower part of the casing. This damping liquid finds its way through a small orifice, past the piston on the lower end of the upper part of the casing when the initial shock of landing is absorbed, and the subsequent action of the ring springs permits the resilient support of the load.

A further object of the invention is the provision of this type of airplane'shock absorber as an elongated member with means at either end for attachment to the fuselage and to the landing gear axle, so that the entire shock absorber casing may serve as a strut to interconnect the axle to the fuselage.

Further objects and advantages of my invention will more fully appear in the following description of the preferred embodiment as illustrated in the drawing, in which Figure 1 is a central section through the shock absorber and Figure 2 is a perspective view of the application of the shock absorber to an airplane.

Referring more particularly to the drawing by reference numerals, the airplane shown in Figure 2 designated generally I, is provided with two landing wheels 2, each of which is supported with an axle member 3 each of which is hinged at its inner end to the lower central portion of the fuselage. The axles 3 which support the wheels are formed of a V-shape so that the wheels are braced in a fore and aft direction in a rigid manner. The wheels 2 are permitted to yield vertically by means of the shock absorber casing 4 which acts as a strut between the connection 5, at the fuselage and the connection at the lower end of the casing where it is attached to the apex of the V of the axle 3.

The shock absorber I is formed of an upper casing member 6, formed as an elongated cylinder closed at its upper end and telescopically engaging the upper end of the lower casing member I. The lower casing member. 1 is permanently connected at its lower end to an end plate 8 in which is fastened the spherical end connection 9. It will be understood that the spherical end con nection or ball 9 forms part of the ball and socket joint which is provided to interconnect the, casing to the landing wheel axle. The upper end of easing member I is threaded into a casting l0, and a lock nut l l holds these two parts assembled. The casting III is provided with a thread l2 which receives the gland nut l3 by means of which the packing M is held in place. This packing forms a, fluid tight connectionso' that the lower end of the upper casing 6 may move up and down within the gland nut l3, which is comparatively long so that the joint between the two members 6 and I may withstand bending strains.

The lower end of the upper casing member 6 is provided with internal threads l5 which receive threads provided in the cylindrical extension l6 of the plunger or piston II. The plunger or piston I! is thus fastened securely to the easing member 6 and is prevented from becoming loose due to rotation by the cotter pin IS. A small passage I9 is provided in the side of the cylindrical member l6 as shownand a passage 20 closed by a screw member 2| is provided in the casting l through which oil may be supplied to the casing.

The upper end of the casing member 6 is permanently fastened to an end cap 22 which rigidly holds the ball 23 which is adapted to cooperate with the socket at the point where the casing is attached to the fuselage. a

The lower casing member 1 supports a series of endless or integrally closed rings there bein a number of inner rings 24 and outer rings 25 which are provided with tapered frictionally and telescopically engaging surfaces. The taper provided on these'friction surfaces is of a character which places the rings under inter-dependent frictional and radial tensional and compressional strains when the series is compressed in the direction of the main axis of the casing. The internally tapered rings 25 are made of a high tensile strength material such as steel and the externally double tapered rings II are constructed of a material such as duralumin which has a high compressive strength weight ratio. The rings are compressed together by a follower 26 which is shown in its normal position against the bushing 21 which is fixed within the upp r end of the casing member I. The follower 28 is moved downwardly to compress the rings together, by the piston member H which engages the follower after the piston has traveled through a small distance from the position shown in Figure 1. The lower casing member I is full of a suitable damping fluid, preferably a liquid 28 such as oil. and this lower casing member I is of substantially larger diameter than the upper casing member 6 which, however, is of greater length than the lower casing member. The piston ll may therefore travel downwardly within the easing member I so as to engage the follower 26 and compress the rings to their utmost before the upper casing member 6 is completely filled with the damping oil. This oil .finds its way through a suitable leak around orfthrough the piston l1 and for this purpose a small orifice 29 is provided in the center of the piston. This orifice is of such size that the initial major shock of landing is absorbed without rebound mainly in the squash of the damping liquid as the oil flows through the restricted orifice into the upper casing member 8. The initial shocks of landing which are even greater than usual, are absorbed first by the squash oi the damping liquid and then by the friction ring springs which are compressed as previously mentioned. The springs yieldingly support the load without appreciable rebound, as' the rebound is largely absorbed by the friction between the rings and by the restriction of the opening 29 provided for'the flow of damping liquid which retards down-flow as well as up-fiow, of liquid. After the initial shock of landing has been absorbed the airplane is resiliently supported by means of the friction rings or springs which absorb the minor shocks as the airplane runs along the ground.

It will thus be apparent that a shock absorber has been provided for an airplane, which will offer a minimum of resistance to the wind and which will serve not only as a shock absorber but also as a strut for inter-connecting the fuselage and the landing wheel. The casing which thus acts as a strut contains within a comparatively small diameter both the liquid damping means for absorbing the initial shock of landing and the friction rings for resiliently supporting the load.

I do not intend to be limited to the precise form of construction which has been shown herein for purposes of illustration of my invention.

, I claim:

1. In a combination in an airplane shock ab- V scrber, a liquid damping means for absorbing the initial shock of landing and a resilient frictional device for resiliently supporting the load and effective to resiliently support the load only after initial shock of landing has been absorbed by said liquid dampin'g means.

immersed in the liquid therein for resiliently supporting the load, and effective to resiliently support the load only after the major initial shock of landing has been absorbed by said liquid damping means.

3. In combination in an airplane shock absorber, a casing, a liquid damping means therein for absorbing the major initial shock of landing, and a resilient device therein for resiliently supporting the load, said device comprising a series of closed rings having complementary similarly tapered friction surfaces,- such as to perm t com pression and rebound of the spring.

4. A shock absorber for airplanes comprising an elongated casing member formed of upper and lower telescoping sections, a quantity of damping fluid in the lower section, a piston member at the lower end of the upper section, a bypass orifice for said damping fluid, and a series of inter-engaging complementary friction members within the lower section adapted to be resiliently compressed by said piston member upon application of the load.

5. A shock absorber for airplanes comprising an elongated upper casing member, a lower casing member normally located below the level of said upper member, a quantity of damping liquid in said lower member, a series of ring springs having inter-engaging tapered frictional surfaces within said lower member, a member fixed to the lower end of said upper casing member adapted to act on said springs to compress the same upon application of the load, and a bypass to permit a limited flow of liquid from the lower to the upper casing member. i

6. A shock absorber for'airplanes comprising an elongated upper casing member, a lower casing member normally located below the level of said upper member, a quantity of damping liquid within said lower member, a series of ring springs having inter-engaging tapered frictional surfaces within said lower member, a follower fixed to the lower end of said upper casing member adapted to act on said springs to compress the same upon application of the load, and a bypass to permit a limited flow of liquid from the lower to the upper casing member, the upper casing member being of substantially greater length and smaller diameter than the lower casing member.

7. A shock absorber comprising an elongated casing formed of an upper and a lower section, a quantity of damping liquid substantially filling the lower section, a series of ring springs having tapered inter-engaging friction surfaces within said lower section, and a piston member normally located a substantial distance from the end of the in claim 6, said upper casing member having a joint member at its upper end adapted to be connected to the fuselage, and said lower casing member having a joint member at its lower end adapted to be connected to the wheel axle.

9. A shock absorbing strut comprising liquid damping means including cylinder and piston for absorbing initial shocks without substantial rebound, and additional means for resiliently receiving additional shocks and ineffective during the absorption of said initial shocks, said additional means located wholly within said cylinder and adjacent the casing wall' thereof and arranged for direct piston engagement.

10. In a shock strut of the class described, in combination, a cylinder, a piston movably received in said cylinder, liquid damping means for absorbing an initial shock without substantial rebound, and spring means for resiliently restraining movement of the piston and efi'ective path of movement of said piston said cy,

prevent rebound only after large degrees of movement of the piston within the cylinder, said spring means lying in the base of said cylinder and wholly therewithin and "adapted for direct engagement by said plstoll.-

11. In a device of the class described adapted to absorb the energy of exerted compressive forces, dashpot means including an orificed piston and cylinder for initially absorbing the energy of an exerted compressive force at a substantially constant rate, and additional load supporting spring means located in the cylinder brought into operation by direct contact with the piston when the first means has reached a predetermined positioning under the influence of said compressive forces for additionally absorbing energy of compressive forces.

12. In a device of the class described adapted to absorb the energy of exerted compressive forces, means including a cylinder and piston for initially absorbing the energy of an exerted oompressive force without substantial rebound, and additional 'load supporting resilient means brought into operation when the first means has reached a predetermined positioning under the influence of said compressive forces for additionally absorbing energy of succeeding compressive forces in a resilient manner, said resilient means being located adjacent the cylinder wall wholly within the cylinder and below the piston.

13. A shock absorber of the class described comprising liquid damping means for absorbing shocks, and a resilient frictional device normally immersed in the liquid for resiliently supporting a load.

14. In an airplane shock absorber, a normally upright casing, liquid damping means in said casing for absorbing shocks, and a resilient frictional spring device normally immersed in the liquid tending to resiliently support the load, said liquid damping means acting to restrict rebound of the spring device.

15. A shock absorbing strut comprising liquid damping means including cylinder and piston for absorbing shocks without substantial rebound, and resilient means wholly within said cylinder arranged directly in the path of movement of said piston for resiliently receiving additional shocks after initial movement of the piston.

16. A shock absorber comprising liquid damping means including cylinder and orificed piston for absorbing shocks and dissipating the energy thereof, and a load supporting resilient means arranged in the path of movement of said piston for resiliently receiving shocks after initial movement of the piston.

17. An aviation shock strut comprising a cylinder, damping liquid therein, an orificed adapted to reciprocate therein, and resilien load supporting means in the cylinder arranged the piston and liquid adapted to of the resilient means. l

18.,A shock' strut comprising a cylinder, an orificed piston movable therein, damping liquid in the cylinder, and resilient load supporting means in the cylinder arranged in path of movement of said piston and adapted to be engaged thereby after initial movement thereof.

19. A shock strut comprising compressive members including a cylinder and a piston having an orifice, a resilient load supporting spring movement of said piston.

21. A shock absorbing strut comprising a cylinder, a piston having an orifice, a resilient spring arranged concentrically in said cylinder and adapted to be compressed by said piston, and damping liquid completely filling the cylinde 22. In a shock absorbing strut, a cylinder, a load supporting spring located in the bottom thereof, a sleeve in the top of the cylinder, a retaining ring between the sleeve and spring, an orificed piston coacting with damping liquid in said cylinder slidably engaging the sleeve and adapted upon downward movement to engage said retaining ring and compress the spring.

23. An aviation shock strut comprising a pair of telesc'opic members closed at their outer ends, a leak tight gland on one member, a piston having an orifice on the other, damping liquid filling the member having the gland, and a load supporting spring immersed in the fluid and arranged directly in the path of the outer annular area of said piston so as to be engaged thereby after initial shock absorbing movement thereof.

24. A shock absorbing strut comprising liquid ton engagement.

25. A shock absorbing strut comprising a cylinder, a piston having an orifice slidable within said cylinder, a tubular member slidable within said cylinderand secured to said piston, a packing carried by saidcylinder and engaging said member, a resilient loadsupporting spring arranged concentrically in said cylinder and adjacent the casing -wall thereof and adapted to be compressed by said piston and damping liquid completely filling the cylinder.

26. In a shock absorbing strut, a cylinder, a load supporting spring located in the bottom thereof, means in the cylinder adjacent the top of the spring for retaining the spring in place in the bottom portion of the cylinder; an orificed piston coacting with damping liquid in said cyl- FREDERICK a. WEYMOUTH. 

